1. Technical Field
The present invention relates to a to a poly(p-xylylene)-based polymer having a low dielectric constant as a low loss dielectric (LLD), and an insulating material, a printed circuit board and a functional device using the same and more particularly, to a poly(p-xylylene)-based polymer including at least one repeat unit expressed by the following formula (1):

wherein, at least one of R1, R2, R7 and R8 is independently substituted or unsubstituted C6-C20 aryl;
the rest of R1 to R8 are each and independently H, substituted or unsubstituted linear C1-C3 alkyl, or substituted or unsubstituted branched C1-C3 alkyl; and
n is an integer of 400 to 900,
and an insulating material, a printed circuit board and a functional element using the same.
2. Description of the Related Art
Growth of integrated circuits has allowed miniaturization of circuits and further allowed multifunctional and high performing products with high integration. Accordingly, interposers, packages, and printed circuit boards, etc. for providing electrical connection between integrated circuits mounted and another component have moved toward high integration. All components have been mounted on the surface of a board in conventional multilayer boards. However, there has been a large demand for embedded PCBs with higher densities, greater capabilities and smaller sizes in which a great number or a part of components are incorporated into internal layers. A package or board providing size reduction by 3-dimensional mounting of components and improved electrical performance at a high frequency is called as an embedded PCB.
Embedded printed circuit boards are multilayer printed circuit boards in which semiconductors and passive components are mounted and have high density, high performance and/or high frequency characteristics. Minicaturization of integrated circuits with high density (large-scale integration) has been developed for the demand of smaller, thinner and lighter weight of electronic devices and has been possible with ultra-fine wirings of integrated circuits. However, due to concerns of reducing electric power consumption and mounting of chip components, embedded PCBs, in which passive components are used and of which passive components are directly incorporated into internal layers, have been more demanded. Low loss dielectric (LLD) is a board material to be used as insulating materials or functional devices (e.g., filter, etc.) of radio frequency embedded boards. Lower cross talk and lower transmission loss is required for electronic devices with smaller in size and higher frequency. Accordingly, there is a demand for researches on new insulating materials with low dielectric property and low loss and thus suitable for high frequency packaging and modules, etc. Materials having high Q value for embedding a filter and the like inside the package are also required for miniaturization. Low loss dielectrics play roles of insulating between wirings or between functional devices in the embedded PCB and of maintaining the strength of packages. Much higher-density wirings are also required in packages along with using ultra-fine wirings and operation of high density integrated circuits at higher frequencies. Since such high density wirings may cause noises between wirings, dielectric constant of insulating materials, parasitic capacitance and loss of dielectric have to be lowered to reduce insulating damages.
Benzocyclobuten (BCB) has been used for its excellent properties but cannot be suitable for printed circuit boards due to high cost. Liquid crystalline polymer (LCP) has also excellent properties but causes problems in the processing of printed circuit boards due to characteristics of thermoplastic resin. Therefore, it is highly demanded to develop new materials having insulating properties and processability.